Ink jet inks many times provide marginal print quality. This is so, because water-based ink jet inks are generally incompatible with paper, having poor penetration and drying characteristics with respect to the paper.
On the other hand, oil-based inks which are more compatible with paper, have low surface tension and usually provide ink dots which are too large to give good print quality.
The present invention seeks to formulate ink jet inks which can provide small, circular dots on many paper media. These small circular dots will produce characters having good edge definition, and contrast, and hence, characters of good print quality.
The present invention proposes to use waxes as additives to ink fluids or which themselves serve as base fluid components of ink jet inks. The waxes of this invention are preferably natural waxes, or combinations thereof.
Wax-containing ink jet inks are usually solids or semi-solids at ambient temperature, and therefore, require to be discharged from an ink jet apparatus at elevated temperatures. The heated ink fluid will solidify when it comes in contact with its paper target. The rate of solidification of the wax-containing ink will control the degree of penetration into the paper, usually a small circular dot will result. As a general rule, inks containing wax as a major component thereof, will have less penetration into the paper than inks containing additive amounts of wax.
A definition of "waxes" can be found in Industrial Waxes by H. Bennett; Volumes 1 and 2; Chemical Publishing Company, Inc., New York, NY (1975). Bennett defines a wax as "an unctuous solid with varying degrees of gloss, slipperiness and plasticity, which melts readily".
Natural waxes may be of vegetable, animal, or mineral origin. Modified waxes are natural waxes that have been treated chemically to change their nature and properties. Synthetic waxes are made by the reaction or polymerization of chemicals. Compounded waxes are mixtures of various waxes or of waxes with resins or other compounds added thereto.
Natural waxes show variations in properties which may be due to soil, climate, age, oxidation, or impurities. Thus, small differences in properties exist for a particular wax. For most industrial uses, these small differences are not critical.
There is considerable misunderstanding as to the nature and classification of fats, waxes, gums, and resins. For example cocoa butter, although it is actually a fat, is commonly considered as a wax because of certain characteristic properties. On the other hand, wool wax, derived from lanolin, is technically a wax but, because of its properties, it is usually considered as a fat. Kauri gum is commonly called a wax; and so on.
The definition of "natural wax" for purposes of this invention is defined as: A wax or mixture of waxes of natural origin which can be either vegetable, animal or mineral, or which can be a chemically modified derivative thereof, or at least one wax of natural origin in combination with other types of wax or ink ingredients.